sv_map and change_map commands should list available maps

[Chairn]

As proposed by @Robyt3 in https://github.com/ddnet/ddnet/issues/5711 (relevant comment https://github.com/ddnet/ddnet/issues/5711#issuecomment-1208390586) and relevant upstream PR https://github.com/teeworlds/teeworlds/pull/3041

[Robyt3]

The backend/protocol from https://github.com/teeworlds/teeworlds/commit/bc38f677506bb0244e4c3f986332f9bb72a8c4b9 has to be ported first.

The additional sv_maplist setting can be ported from https://github.com/teeworlds/teeworlds/pull/2937.

Also https://github.com/teeworlds/teeworlds/pull/3054, https://github.com/teeworlds/teeworlds/pull/3084 and https://github.com/teeworlds/teeworlds/pull/3083.